Literature Review Of Flooding And Flood Risks Environmental Sciences Essay

Literature Review Of deluge And outpouring lamp Risks Environmental Sciences essayThe concept of runing has a multi-disciplinary definition based on the touch on of the defining discipline. However, out melt down is generally taken to include any vitrine where land not normally cover by water becomes covered by water (FWMA, 2010 Pt 1). In recent decades there draw been raging scientific and media debates on likely agitates in make full regimes generated by land-use changes and humor change (Ranzi et al, 2002). The crux of near of these debates is centred on the simulated chance from such bombardment events. These guesss argon tie in to human health, infrastructure, socio-economic well-being of abnormal individuals and damage too to archaeological relics. Methods of evaluating and assessing onslaught risk turn over been true in the field of insurance, technological and environmental fields (Molak, 1997 Jones, 2001). Although river flooding is frequently related to natural disasters, the impacts of human activities such as urbanization have been observe by many scholars (Sala and Inbar, 1992 Kang et al, 1998 Ranzi et al, 2002). Flood risk is expressed in terms of the probability of authorizerence of adverse set up of flood related hazards and vulnerability with dominance consequences (Mileti, 1999 Merz, et al, 2007 FWMA, 2010). Although a number of approaches have been tested for flood events prediction, hydraulic mouldings have been specifically radiation patterned to predict flood photoflood (Horritt and Bates, 2002). Consequently, in the development of an effective and efficient flood risk instruction strategy hydraulic, hydrologic and socio-economic factors must be taken into consideration (Merz et al, 2007).2.2 Urbanisation and FloodingUrbanization and flooding are intricately linked in twain developed and developing countries. Increasing population growth and continued urban expansion has led to a reduction in surface permea bleness which invariably profits surface runoff in the absence of alleviating urban drain design (Kang et al, 1998 Parker, 1999 Ranzi et al, 2002). Although the UK has only small rivers by world standards, with the tendency for smaller-scale floods to occur (Wheater, 2006), considerable economic and infrastructural way outes arise from urban flooding (Mark et al, 2004). This loss is world-shatteringly higher in smaller river bank communities. For instance, Wheater (2006) notes that the 24hr rain in Carlisle on the 8th and 9th of January 2005 resulted in the loss of two lives, an estimated damage of 450 trillion and flooding of over 2000 properties when the flood defences were over-topped. The engineering and design of flood defences are based on hydrological and hydraulic models of river catchments. Hydrological models simulate surface runoff from rainfall while the hydraulic model describes structural controls of the river system (Kite, 2001 Mark et al, 2004 Kidson et al, 20 06 Heatlie et al, 2007).We close down that urbanization can represent a very significant increase in flood risk at small catchment scale, but that the effects are commonly mitigated, to a greater or lesser extent, by design measures. The impacts of effects at larger scales are complex and face on the relative magnitude and timing of sub-catchment responses and the performance of mitigation strategies. congeneric effects of urbanization on flooding are expected to drop-off with increasing storm return period, but the performance of mitigation strategies for events rarer than the design criteria adopted is largely unexplored.2.3 Global warming and FloodingThough it is tacit difficult to attribute global warming preserve this century to the enhance greenhouse effect and the resultant increase in observed rainfall (Reynard et al, 2001 Robson et al, 1998), the recurrent incidence of floods and their magnitude in the UK in recent propagation have raised major concerns that the effe ct of climate change is already being felt across the country (Robson, 2002). Milly et al, (2002) bugger offd the theory Global humour mock ups have been utilise to determine the likelihood of increased flood risk from global warming. Reynard et al (2001) used the CLASSIC (Climate and LAnd use Scenario mannikin In Catchments model) continuous die hard simulation model to assess the potential impact of climate and changes in land use on the flood regimes of the Severn and Thames rivers. They found that for the 2050s, the climate change scenarios results in an increase in twain the oftenness and magnitude of flooding events in both rivers. Similarly, Milly et al (2002) observed that the frequency of great floods increased significantly during the twentieth century. Accordingly, the statistically significant positive trend in the risk of floods was consistent with the results from the climate model (Milly et al, 2002). Roy et al (2001) investigated the impact of climate change on summer and autumn flooding on the Chateauguay river basin. Their study reveals serious potential increases in the wad of runoff, maximum discharge and water level with future climate change scenarios for a three 20-year periods spanning 1975 1995, 2020 2040, 2080 2100.2.4 pattern of Flood eventsThe simulation of extraordinary tend events characterized by high hydraulic risk has posed serious problems for polity makers, engineers and environmentalists around the world. The use of 1-D modelling for predicting flood risk generated by events of contrasting return period or multiple land use and climate change scenarios is widespread (Lin et al., 2005 Mark et al., 2004 Horritt and Bates, 2002 Mark et al., 2004 Lin et al., 2005 Hall et al, 2005). In their study, Bates and De Roo (2000) show the use of a 1-D model type storage cell called LISFLOOD-FP to produce designated channel cells for channel routing and uniform flow formulae for floodplain routing, through the bring of d iscrete raster-based analysis derived from a DEM at 100, 50 and 25m resolutions respectively and utilize to a major flood on a 35km r distributively of River Meuse. Syme (2001) notes that in addition to rapid wetting and drying, the strength of TUFLOW is its powerful 1D linking options, modelling of hydraulic structures, treatment of levees and embankments, effective data handling and quality control outputs.Horritt and Bates (2002) discontinue that HEC-RAS models correctd against discharge gave good flood predictions of inundated area on a 60km reach of the river Severn, UK.Reed and Robson, (1999, cited in Dawson et al., 2006) emphasise that many flood estimation problems were likely to arise at ungauged sites due(p) to the unavailability of flood peak data recorded in the UK Flood Estimation Handbook (FEH). The FEH is produced by the Centre for Ecology and Hydrology with information somewhat River catchments in the UK such as, rainfall frequency estimation, statistical proce dures for flood frequency estimation, rainfall-runoff and catchment descriptors. Dawson et al., (2006) used the Artificial Neural Networks (ANN) technique to estimate flood statistics for un-gauged catchments (for most of the River catchments in the UK). The index flood analysis from the ANN results produced a comparable truth to that obtained from the Flood Estimation Handbook (FEH), but the flood estimation for each catchment was carried out for only a 10, 20 and 30 year flood event period giving room for short term flood defence preparation thereby incurring future expense on what can be predicted for up to 1000 years.A study by Yang et al (2002) on prediction of flood inundation and risk, using GIS and hydrodynamic model showed the ability to use a DEM manipulated in GIS and translated into MIKE21 (a modelling environment). In the study, different scenarios were evaluated and results translated to the GIS environment for visualization and analysis on flood events for an estimat ed 100-year flood return period. However, Yang et al, stressed that there were no real means to calibrate the simulations from the modelling output, as flow and stage data were rarely recorded for flood events and also, compare between outputs from MIKE21 and MIKE1, the former, being an upgrade of the latter.2.5 One-Dimension ISIS flood ModellingThe ISIS model has been used extensively in modelling inundated flow regimes of rivers across the UK (Heatlie, et al. 2007). The Manchester Ship Canal, a 58 km long river hardened in North West England and constructed in 1894 to include the navigable cave in of River Irwell (including River Irwell at Radcliffe, Bury) was one of the last major watercourses in the United realm to be analysed with hydraulic modelling techniques (Heatlie, et al. 2007). In preparation of an indicative flood mapping (IFM), the EA used an unsteady ISIS 1-D hydraulic model for the mapping of a 47km length of the Upstream Bristol Forme catchment to define areas at flood risk in 2002 (Syme et al, 2004).According to past studies (Costa-Cabral and Burges, 1994 Bodis, 2007 Rees, 2000) it is evident that the use of Digital Elevation Model (DEM) in flood model creation have played a big role in the successful presentation of hydrological and topographical drainage basin data analysis (Peckham, 1998) because it depicts an array of elevations across the basin at regularly spaced intervals (Cunha, 2009). This eliminates the assumption that the catchment or area is a prone surface without compliances.In research carried out by Sansena Bhaktikul (2006) on the integration of hydraulic modelling and GIS towards the study of river the Mae Klong (Bangkok, Thailand). The runoff frequency analysis was used in the creation of a flood risk map. The study also showed that the results from the simulation carried out, was properly presented in GIS and DTM format, by making use of the contour and river spot height data. Sansena Bhaktikul (2006) conclude their study by suggesting that further studies be done on larger basins by dividing them into sub-basins and the network link to mix them should be introduced to have an overview of the basin. The runoff flow in flood plains, river bring and man-made structures are important factors in the study of runoff flow behaviour prediction of flood areas, they added, and thus further studies are thusly recommended to include rainfall runoff models in upriver and unsteady areas.2.6 needTo develop an appropriate one-dimensional ISIS hydraulic model of flood events that includes upstream catchments of the River Irwell and produce a flood map to predict flood extents an essential flood event period.2.7 Research QuestionDoes the inclusion of upstream catchments remedy the net flood prediction model of the river Irwell?What areas are most undefendable to flood risk in Radcliffe, Bury?To what level should the flood defences be built around the Radcliffe area?